LOS ANGELES — California officials on Monday unveiled a major overhaul of a controversial plan to build a high-speed rail system in the state, slashing the cost by some $30 billion, to $68.4 billion, and addressing other criticisms of the massive project.

The new plan must now receive a final blessing from the California High Speed Rail Authority before going to the state legislature, which has to approve the release of the first chunk of the nearly $10 billion in rail bond funds voters approved in 2008.